Igniter air shield

ABSTRACT

A burner assembly for use adjacent an igniter element in a gas appliance includes a top plate configured to form the geometric top half of at least one burner, and a bottom plate configured to form the geometric bottom half of at least one burner. The top plate and the bottom plate are joined together to form a burner and a burner carryover. An igniter air shield extends from either the top plate or the bottom plate such that the igniter air shield diverts secondary combustion air flowing around the burner and the adjacent igniter element.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/613,735 filed Mar. 21, 2012, the contents ofwhich are incorporated herein by reference thereto.

BACKGROUND OF THE INVENTION

The invention relates generally to furnaces having igniter elements and,more particularly, to furnaces having shields for the igniter elements.

In furnace applications, igniters commonly include an igniter element.The igniter is positioned such that the “hot spot” of the igniterelement, or the portion of the igniter element that reaches the hottesttemperature, is placed directly in the mixture of fuel and air to createthe point of ignition. If the igniter is not at a temperature hot enoughto cause the fuel and air mixture to combust, the fuel flow to thefurnace will automatically shut off. A predominant cause of igniterelement cooling is secondary combustion airflow. Secondary combustionairflow moves quickly past the igniter causing the igniter element tocool to a temperature below that required to ignite the surroundingfuel. Systems using less power are also susceptible to igniter elementcooling because less power is used to heat the igniter. Some furnaceapplications require the furnace to use a lower voltage power supply,such as 98V for example, rather than the typical 110V; therefore lesspower is applied towards heating the igniter than in a full voltagesystem. If the igniter is too cool to ignite the fuel and air mixture,no heat will be produced from the furnace.

BRIEF DESCRIPTION OF THE INVENTION

According to an exemplary embodiment of the invention, a burner assemblyfor use in a gas appliance is provided including a top plate configuredto form the geometric top half of at least one burner and a bottom plateconfigured to form the geometric bottom half of at least one burner. Thetop plate and the bottom plate are joined together to form a burner anda burner carryover. An igniter air shield extends from either the topplate or the bottom plate such that the igniter air shield divertssecondary combustion air flowing around the burner.

According to another embodiment of the invention, a burner unit isprovided including a burner assembly having a plurality of axiallyaligned burners. The burner unit also includes a burner box forreceiving the burner assembly. An igniter assembly is mounted such thatthe igniter element is adjacent the burner assembly. The igniterassembly includes an igniter element extending from an insulative body.An igniter air shield extends from a portion of the burner assembly suchthat the igniter air shield diverts secondary air flowing around theburner assembly away from the igniter element.

According to yet another embodiment of the invention, a furnace isprovided including a burner assembly having a plurality of axiallyaligned burners. A burner box receivers the burner assembly. An igniterassembly includes an igniter element connected to an insulative body.The igniter assembly is mounted such that the igniter element isadjacent the burner assembly. An igniter air shield, extending from theburner assembly, diverts secondary air flowing around the burnerassembly away from the igniter element.

These and other advantages and features will become more apparent fromthe following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWING

The subject matter, which is regarded as the invention, is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other features, and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIG. 1 is a perspective cut away illustration of a gas furnace inaccordance with an embodiment of the invention;

FIG. 2 is a perspective view of a burner unit in accordance with anembodiment of the invention;

FIG. 3 is a front view of a burner unit in accordance with an embodimentof the invention; and

FIG. 4 is a cross-sectional view taken at line 4-4 of FIG. 3 inaccordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a perspective cutaway view of a gas-fired appliance, such as afurnace 10. The furnace 10 includes burner assembly 14, burner box 12,gas valve 18, heat exchanger assembly 20, exhaust vent pipe 28, induceddraft blower 30, inducer motor 32, thermostat 34, pressure switchassembly 42, and furnace control 50. In some embodiments, the furnace 10may additionally include a combustion air pipe 16, a condensing heatexchanger 24, and a condensate collector box 26.

Burner assembly 14 is mounted within burner box 12 and is supplied withcombustion air. As will be discussed in more detail below, the burnerassembly 14 includes a gas manifold 36 with a gas orifice 38 (see FIG.2) arranged at one end. Fuel gas is supplied to burner assembly 14through gas valve 18, which may be a solenoid-operated gas valve, and isignited by an igniter assembly 160 (see FIG. 2). The gases produced bycombustion within burner assembly 14 flow through a heat exchangerassembly 20, which includes a primary or non-condensing heat exchanger.In one embodiment, the heat exchanger assembly 20 additionally includeseither a secondary or condensing heat exchanger 24, or a condensatecollector box 26, or both. The gases are then vented to the atmosphereby inducer motor 32 through exhaust vent pipe 28. The flow of thesegases, herein called combustion gases, is maintained by induced draftblower 30, which is driven by inducer motor 32. Inducer motor 32 isdriven in response to control signals that are generated by a furnacecontrol circuit located within furnace control 50, in response to thestates of the pressure switch assembly 42, and in response tocall-for-heat signals received from thermostat 34 in the space to beheated.

Air from the space to be heated is drawn into furnace 10 by blower 52,which is driven by blower motor 54 in response to control signals thatare generated by furnace control 50. The discharge air from the blower52, herein called circulating air, passes over the heat exchangerassembly 20 before being directed to the space to be heated through aduct system (not shown).

Referring now to FIGS. 2 and 3, an exploded view and a front view of aburner unit 11 are illustrated. The burner unit 11 includes a burner box12 and a burner assembly 14 that mounts within the burner box 12. Theburner box 12 includes a top wall 110, a bottom wall 112, and opposingside walls 114. Disposed horizontally along the inside surface of eachof the opposing side walls 114 is an elongated opening 116 for receivingthe burner assembly 14.

The burner assembly 14 includes a plurality of parallel and equidistantburners 130. In the exemplary embodiment portrayed in the FIGS., theburner assembly 14 includes four burners 130. However, the burnerassembly 14 may include any number of burners 130. In an exemplaryembodiment, the plurality of burners 130 is formed from two stamped flatmetal plates, a top plate 120 and a bottom plate 122. The top plate 120and the bottom plate 122 of the burner assembly 14 are stamped so thatthe top plate 120 contains the geometry of the upper half of each burnerand the bottom plate 122 contains the geometry of the lower half of eachburner. Disposed between each burner half is at least one burnercarryover 147 to assist in the ignition process. The plates 120, 122thus divide the burners 130 and burner carryovers 147 symmetricallyalong the central axis Z of each burner 130 so that when the plates 120,122 are assembled in face to face contact, the overall shape of eachburner 130 is produced. Top and bottom plates 120, 122 may be fastenedtogether by any suitable means so that the opposed flat surfaces of theplates 120,122 are held in close intimate contact along the length andbreadth of the plates. Joining the top plate 120 and the bottom plate122 creates a horizontal plane extending through the entire burnerassembly 14 and through the center of each of the plurality of burners130 and burner carryovers 147.

Each burner 130 within the burner assembly 14 has a fuel port 132 at afirst end of the burner 130. The fuel port 132 is a cylindrical elementthat aligns a burner 130 with a respective fuel supply to directpressurized fuel into the burner 130. The fuel port 132 of each burner130 is positioned adjacent to and in axial alignment with a tubularnozzle 138. Each nozzle 138 has a flared inlet end 134 and a cylindricaloutlet end 140. A flame retainer housing 142 is integrally joined to theoutlet end 140 of the tubular nozzle 138 and contains a generallycylindrical flame retainer 144. The flared inlet end 134 has a largerdiameter inlet opening than the fuel inlet opening defined by the fuelport 132. An opening 146 is stamped into each of the plates 120, 122between the fuel port 132 and the inlet 134 to the tubular nozzle 138.Each opening 146 is sufficiently large so that an unimpeded airflow willbe available to support the combustion when the burner is operating atcapacity. The burner carryovers 147 are sized to sufficiently carry theflame to the exit of each flame retainer 144 during the ignitionprocess.

A support piece 150 extends perpendicularly from the top surface 110towards the bottom surface 112 of the burner box 12. Fastened to thissupport piece 150 is an igniter mounting structure 152 having a hole inwhich an igniter assembly 160 is inserted. The support piece 150 and theigniter mounting structure 152 are positioned such that the mountedigniter assembly 160 is adjacent an outlet 140 of a burner 130 locatedat an end of the burner assembly 14. The igniter assembly 160 includesan insulative body 162 and an igniter element 164 extending from withinthe insulative body 162. The igniter element 164 is arranged to providea hot surface to the outlet section of the burner carryover 147 at startup. The igniter element will ignite the primary air/fuel mixture movingthrough the burner 130 and burner carryover 147 and propagate the flameto the exit of each flame retainer 144.

As the fuel is injected through the fuel port 132, air also enters theburner 130 due to the difference of the diameter of the inlet and thediameter of the fuel port 132. The fuel and air combine at the inlet 134of the tubular nozzle 138 to create a primary fuel/air mixture. As theprimary fuel/air mixture flows through the burner 130 and the burnercarryover 147, the primary fuel/air mixture contacts the hot surfaceigniter element 164 causing the mixture to ignite at the burnercarryover 147 closest to the igniter element 164. The flame is thencarried across each burner carryover 147 and the exit of each flameretainer 144. Secondary combustion air (See FIG. 4) flows around theoutside of the burners 130 and burner carryovers 147 and gradually mixesinto the flame extending axially downstream from the exit of the flameretainers 144. At the exit of the burner carryovers 147, ignited fuelspreads laterally to ignite the other burners 130 in the burner assembly14. A flame sensor 168 is also mounted to the burner box 12. The flamesensor 168 determines if all of the burners 130 in the burner assembly14 are lit. If not all of the burners 130 have ignited within a givenperiod of time, the flow of fuel to the burners 130 is shut off.

Referring now to FIGS. 3 and 4, arrows A and B represent secondarycombustion air flowing around the top and bottom of the burner assembly14 in the direction of the igniter element 164. An igniter air shield170 extends from the burner assembly 14 adjacent first burner 130 andigniter element 164. The igniter air shield 170 diverts the secondarycombustion air away from the igniter element 164 to reduce the coolingof the igniter element 164. The igniter air shield 170 also improves thestability of the flame exiting the burner carryover 147 closest to theigniter element 164. Therefore, the igniter air shield 170 improves therobustness of the ignition process within the furnace 10.

The igniter air shield 170 may be formed integrally with the burnerassembly 14. In an exemplary embodiment, if the burner assembly 14includes a stamped metal top and bottom plate 120, 122, the igniter airshield 170 may be formed as part of either the top or bottom plate 120,122. To form the igniter air shield 170 as part of the bottom plate 122,for example, the stamped metal will include an additional area extendingbeyond the edge forming the outlet 140 of each burner 130. Thedimensions of the area forming the igniter air shield 170 must besufficient to create a non-turbulent flow or stable flow adjacent theoutlet of the burner carryover 147 closest to the igniter element 164,and the igniter element 164. The area forming the igniter air shield 170is then bent so that a portion of the igniter air shield 170 will extendinto secondary combustion air flow B around the bottom plate 122 todivert it away from the igniter element 164. The angle of the bend ofthe igniter air shield 170 may range from zero to ninety degrees fromthe horizontal plane of the plate. In an alternate embodiment, theigniter air shield 170 may be a separate part that is then attached tothe portion of the burner assembly 14 adjacent the burner carryover 147closest to the igniter element 164. The igniter air shield 170 may beattached by welding, fastening, or any other suitable means.Additionally, a second igniter air shield 170 may extend from the top ofthe burner assembly 14 adjacent the igniter element 164 to divert thesecondary air flow represented by arrow A away from the igniter element164.

While the invention has been described in detail in connection with onlya limited number of embodiments, it should be readily understood thatthe invention is not limited to such disclosed embodiments. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. Additionally, while various embodiments of the invention havebeen described, it is to be understood that aspects of the invention mayinclude only some of the described embodiments. Accordingly, theinvention is not to be seen as limited by the foregoing description, butis only limited by the scope of the appended claims.

1. A burner assembly for use adjacent an igniter element in a gasappliance comprising: a top plate configured to form the geometric tophalf of at least one burner; a bottom plate configured to form thegeometric bottom half of at least one burner, wherein the bottom plateand the top plate are joined to form a burner and a burner carryover;and an igniter air shield extending from one of the top plate or bottomplate such that the igniter air shield diverts secondary combustion airflowing around the burner carryover and away from the adjacent igniterelement.
 2. The burner assembly according to claim 1, wherein the sizeof the igniter air shield is sufficient to create a stable flow adjacentan outlet of the burner carryover.
 3. The burner assembly according toclaim 1, wherein the igniter air shield forms an angle with thehorizontal plane of the burner assembly such that the range of the angleis between zero and substantially ninety degrees.
 4. The burner assemblyaccording to claim 1, wherein the igniter air shield is integrallyformed with the bottom plate adjacent an outlet of a burner carryover.5. The burner assembly according to claim 1, wherein the igniter airshield is fastened to the bottom plate adjacent an outlet of a burnercarryover.
 6. A burner unit comprising: a burner assembly having aplurality of axially aligned burners; a burner box for receiving theburner assembly; an igniter assembly including an igniter element,wherein the igniter assembly is mounted to the burner box such that theigniter element is adjacent the burner assembly; and an igniter airshield extending from a portion of the burner assembly, such that theigniter air shield diverts secondary air flowing around the burnerassembly away from the igniter element.
 7. The burner unit of claim 6wherein the burner assembly further comprises: a top plate configured toform the geometric top half of a plurality of burners; and a bottomplate configured to form the geometric bottom half of a plurality ofburners, wherein the bottom plate and the top plate are joined to form aplurality of burners and burner carryovers.
 8. The burner unit accordingto claim 6, wherein the size of the igniter air shield is sufficient tocreate a stable flow adjacent the igniter element and an outlet of aburner carryover from the burner assembly.
 9. The burner unit accordingto claim 6, wherein the igniter air shield forms an angle with thehorizontal plane of the burner assembly such that the range of the angleis between zero and substantially ninety degrees.
 10. The burner unitaccording to claim 7, wherein the igniter air shield is integrallyformed with the bottom plate adjacent an outlet of a burner carryover.11. The burner unit according to claim 7, wherein the igniter air shieldis fastened to the bottom plate adjacent an outlet of a burnercarryover.
 12. A furnace comprising: a burner assembly having aplurality of axially aligned burners; a burner box for receiving theburner assembly; an igniter assembly including an igniter element,wherein the igniter assembly is mounted to the burner box such that theigniter element is adjacent the burner assembly; and an igniter airshield, extending from the burner assembly, for diverting secondary airflowing around the burner assembly away from the igniter element. 13.The furnace of claim 12 wherein the burner assembly further comprises: atop plate configured to form the geometric top half of a plurality ofburners and a bottom plate configured to form the geometric bottom halfof a plurality of burners wherein the bottom plate and the top plate arejoined to form a plurality of burners and burner carryovers.
 14. Thefurnace according to claim 12, wherein the size of the igniter airshield is sufficient to create a stable flow adjacent the igniterelement and an outlet of a burner carryover from the burner assembly.15. The furnace according to claim 12, wherein the igniter air shieldforms an angle with the horizontal plane of the burner assembly, theangle being between zero and substantially ninety degrees.
 16. Thefurnace according to claim 13, wherein the igniter air shield isintegrally formed with the bottom plate adjacent an outlet of a burnercarryover.
 17. The furnace according to claim 13, wherein the igniterair shield is fastened to the bottom plate adjacent an outlet of aburner carryover.